The satellite based Global Positioning System (GPS) provides useful location information for devices that are equipped with respective GPS receivers. The publicly accessible GPS provides location information that is accurate enough for locating a device and its bearer within a range of a few meters. The actual accuracy users attain depends on various factors, including atmospheric effects, sky blockage, receiver quality, etc. While an accuracy of say two to three or four meters is an impressive achievement, it is not sufficient for discriminatory applications requiring “local area positioning” where two or more devices within close proximity to each other need to be identifiable and discernible on the basis of their location. Examples of such applications include wireless payment at a payment terminal, where individuals in a line up or at neighboring terminals need to be distinguished, or access control based on wireless access token systems, where individuals in front or behind an access control device, such as a door or a gate, need to be distinguished.
US 2011/205969 describes a location system which includes a plurality of beacon transmitters each positioned at a respective location. Each beacon transmitter includes a plurality of antennas positioned in a circular arrangement. Each beacon transmitter is configured to transmit an identification signal having a plurality of reference data and to transmit a directional signal from the plurality of antennas by selecting one of the antennas at a time in sequence around the circular arrangement to simulate a rotating antenna. The location system further includes a receiver configured to receive the identification signals and a plurality of Doppler-shifted directional signals each corresponding to one of the directional signals, wherein the receiver is configured to generate a plurality of time data for each received Doppler-shifted directional signal, and wherein the receiver is configured to determine a location of the receiver using each Doppler-shifted directional signal, each time data, and each identification signal received from the plurality of beacon transmitters.
WO 2016/000121 describes a multiple-layer beacon sweeping method performed by an access node and user equipment. The method comprises at least a first beacon sweeping with a first set of beams and a first coverage area and a second beacon sweeping with a second set of beams and a second coverage area, whereby the first coverage area is larger than the second coverage area.
CN 102170697 describes an indoor positioning method which acquires the signal strength transmitted by a plurality of beacon nodes received by a terminal to be positioned.